This invention relates to remotely controlling AC operated barrier moving systems in response to low voltage AC control signals conveyed by wire from a remote location and, more particularly, to methods and apparatus for improving the control signal range capability between the remote location and the barrier moving system.
Existing barrier control systems, such as garage door or driveway gate systems, typically include a control unit which responds to low voltage AC input signals to open, close, or stop the movement of a driveway gate or garage door. In a normal installation, the control unit at the location of the barrier is connected to one or more switches remotely located in, for example, a residence some distance from a gate to be moved. Low voltage AC, e.g., 24 volts, is applied over wires from the control unit to the remote switches and selectively returned over wires to the control unit by manual operation of the switches. Frequently the wire installed with the system is of small gauge, e.g., 22 gauge, which is run to and from the remote location in a closely spaced bundle and perhaps in a grounded conduit.
Such small gauge wire installation serves to keep the system cost low and provides adequate service for limited distances between the control unit and the remotely located switches. The AC operated control unit, however, requires a minimum of low voltage AC power at its signaling inputs in order to properly respond to control signals. The small gauge, closely spaced wires used in a normal system exhibit a significant reactive component of impedance which reduces the power available at the input of the control unit for control signals. When the distance between the remote switches and the control unit is too long, the available power may not be sufficient for reliable control. It has been found that low voltage AC controlled systems wired as above-described operate satisfactorily over distances of only approximately 80 to 100 feet. Also, over the lifetime of such a barrier control system, aging and possible deterioration of the equipment may reduce the operating distance and make a formerly operating system non-operational. Installing wiring having a reduced reactive component of impedance in new systems and similarly refitting previously installed systems may improve the range of reliable operation but such greatly increases system cost and inconvenience of installation.
A need exists for arrangements which can increase the distance capability between a low voltage AC barrier control unit and remote switches simply and cost-effectively.